Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations only declare readOnlyHint=false, so the description carries most of the behavioral burden. It usefully discloses patch semantics ('Only the fields you pass change') and the normalized coordinate system, but does not explain validation behavior, permissions, what happens on invalid ranges, or what the operation returns.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three short sentences with no wasted text. The core purpose is front-loaded, followed immediately by the important partial-update rule and coordinate-system convention.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 10-parameter mutation tool with minimal annotations and no output schema, the description covers the essential editing model and coordinate normalization. It remains incomplete on timing semantics, animation behavior, permissions, and sibling-tool selection, which matter for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 60%, and the description adds useful meaning by mapping verbs to parameters and clarifying that positions are 0-1 of the frame. It still leaves animation, duration_ms, start_time_ms, and overlay_id without additional semantic explanation beyond their raw schema entries.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb-resource pair (update a sticker overlay) and enumerates supported edit operations: move, resize, rotate, fade, and re-time. It is clear what the tool modifies, though it does not explicitly distinguish itself from nearby siblings such as studio.add_sticker or studio.update_text_overlay.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies this is for adjusting an existing sticker overlay and states that only supplied fields change, which helps guide partial updates. However, it does not explicitly say when to use this instead of add_sticker, update_text_overlay, or delete_element, nor does it state prerequisites such as project lock state or required permissions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.